The melanocortin receptors are seven transmembrane G-protein linked receptors which include the receptors for the peptide hormones ACTH, alpha-, beta- and gamma-MSH. To date 5 melanocortin receptors have been cloned by several laboratories including the laboratory of the PI. The objectives of this study are to investigate the structure of the melanocortin receptors (e.g. amino acids involved in ligand binding and domains critical to signal transduction) and to study physiological processes in which this family of receptors participate. Use of the GCG software is essential to these objectives.